Multihull Watercraft

ABSTRACT

The patent discloses a multihull watercraft with a unique hull configuration providing numerous benefits. By relocating the passenger cabins from the float hulls to the upper hull, the accommodation space and the float hulls may be independently optimized. The new configuration also provides reduced windage, and creates additional deck space for easier boarding, recreational use, and safer access to shore craft. A new sailing rig is also disclosed that is easier to operate and maintain than the conventional Bermuda rig. The entire rig can be rotated with a single winch or control wheel to achieve the optimum angle of attack into the wind.

BACKGROUND OF THE INVENTION

The modern monohull watercraft can be traced back to the hollowed logcanoes used by primitive cultures around the world. The long narrow hullof these ancient boats is a very efficient shape in the water, which isan important feature for a vehicle propelled only by human or windpower. In today's world of limited resources and energy an efficienthull shape continues to be a very desirable feature. For a givendisplacement, a hull with high aspect ratio (the length divided by thewidth) is much easier to push through the water than a hull with lowaspect ratio.

One big disadvantage of a narrow monohull is lateral stability. Thenarrow hull presents a greater risk of capsize, especially forsailboats. Making the boat wider increases the stability, but createsmuch more drag though the water. An alternate solution is to keep thenarrow hull form, but add ballast in the form of a weighted keel. Theheavy ballast adds stability, but the boat is pulled deeper into thewater which increases the water displacement and again increases drag.

Early Polynesians developed a clever solution to the problem ofmaintaining stability in a narrow monohull. The Outrigger canoe adds asecondary hull connected to the first hull by a pair of support arms.This results in a very stable boat that still retains the more efficientnarrow hull form. Modern multihull watercraft (catamarans and trimarans)incorporate this idea to achieve significantly improved performance onthe water.

As the multihull form developed into the 21st century, it continued tooffer many advantages over traditional monohulls, but the design stillhas several inherent problems. There is a conflict between accommodationspace and hull form. The narrow shape of catamaran and trimaran hulls,while highly efficient when moving through the water, also createawkward interior spaces. Humans prefer accommodations with roughlysquare-shaped floor plans, not uncomfortable tunnel shapes that areneither convenient nor inviting for any activity except sleep. Wideningthe hull improves the accommodation space but seriously de-grades theperformance of the boat.

Conventional multihulls have a further problem of awkward boarding anddisembarking. This is particularly true for large catamarans on a sidedock, where the high freeboard (the distance between the deck and thewater) requires a ladder or portable staircase for boarding. The highfreeboard also results in high amounts of lateral windage. Compensatingfor this windage while under way wastes a significant amount of energy,and docking and maneuvering in a tight marina can be difficult as thewind pushes the boat off course.

Conventional multihulls have a further problem of awkward storage anddeployment of a shore craft (dinghy). Storage on deck takes up valuablespace and may also require a crane for deployment. Dinghy davits(typically a pair of metal arms used for both storage and deployment)are also not an optimum solution in terms of convenience and aestheticappeal. In either case, boarding and exiting the dinghy can be awkwardand dangerous because there is no suitable boarding platform.

Conventional multihulls have a further problem of very complicatedsailing rigs. The standard Bermuda rig is difficult to operate andmaintain. The sailor must manage an intimidating profusion of controllines including halyards, main sheet, jib sheets, outhaul, travelers,stays, reefing lines, and more. The sheer number of mechanicalcomponents also makes the system prone to failure.

The present invention addresses all of these problems while providingadditional benefits.

SUMMARY OF THE INVENTION

Unlike conventional multihulls that use the cramped float hulls foraccommodation, the present invention moves the passenger cabins to theupper hull several feet above the water-line. This removes the conflictbetween the accommodation space and the float hull form; each can beindependently optimized without compromising the other. The higherelevation improves interior ventilation, increases thermal isolationbetween the cabins and the water, and provides better view of thesurroundings for both skipper and passengers.

There are four support structures between the upper hull and the floathulls which are designed to reduce windage from the high cross windsthat can be encountered at sea. Each structure is comprised of aplurality of narrow columns that provide mechanical support whileallowing lateral air flow.

In order to maximize the accommodation space, the forward and aftportions of the upper hull (enclosing the private cabins) extendlaterally over the left and right float hulls. The central portion(enclosing the salon, galley, and other common areas) of the main hullis narrower, extending laterally to points inboard of the longitudinalcenterline of the left and right float hulls. This unique configurationcreates space for deck areas on the top side of the left and right floathulls. The low freeboard of the twin decks allow easy boarding anddisembarking to docks on either side of the boat, and safer boarding ofshore craft.

Access to the upper hull is via a staircase from the deck of the left orright float hull. This eliminates the need for portable boarding stairsat the dock; passengers simply step onto the deck of the float hull,then go up the stairs into the upper hull.

The present invention offers an improved method of storing and deployinga shore craft (dinghy). When not in use, the dinghy is stored in acompartment located on the underside of the upper hull. To launch thedinghy, the compartment cover is lowered to provide access to thecompartment via the adjacent float hull deck. The dinghy is moved acrossthe deck and into the water along the outside edge of the hull where itcan be easily and safely boarded. In an alternate embodiment, the dinghymay be lowered directly into the water, where it may be boarded from theinboard edge of the adjacent float hull deck.

The present invention incorporates a new sail configuration that issubstantially easier to operate and maintain in comparison to thetypical Bermuda rig found on most sailboats. The rig includes a forwardsail and an aft sail which can be rotated simultaneously to the optimumposition for the current wind direction. The rotation of the rig can beset by manually turning a single winch, control wheel, or equivalentelectrical means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the multihull watercraft in a powerboatconfiguration (without sails).

FIG. 2 is a perspective view of the multihull watercraft showing animproved embodiment of the upper hull support structures.

FIG. 3 is a top view of the powerboat configuration that shows the upperhull and left and right float hulls.

FIG. 4 is a rear view that shows the dinghy storage compartment doorlowered to a position adjacent to the right float hull, whereby thedinghy can easily be moved out of the compartment, across the top sideof the float hull and pushed into the water for boarding. Thecompartment door is illustrated as being hinged on the inboard side,however an alternative embodiment could lower the entire door (anddinghy) to an altitude matching the float hull deck.

FIG. 5 is a perspective view depicting the deployment of a dinghy acrossthe float hull and into the water where it may be boarded

FIG. 6 is a perspective view showing an alternate embodiment wherein thedinghy is lowered from the under-hull storage compartment directly intothe water for boarding via the deck of the adjacent float hull.

FIG. 7 is a perspective view of the multihull watercraft in a sailboatconfiguration with the basic embodiment of the sailing rig.

FIG. 8 is a detailed view of the sailing rig basic embodiment.

FIG. 9 illustrates an improved embodiment of the sailing rig with theaddition of forward and aft booms

FIG. 10 illustrates further improvements to the sailing rig with theaddition of boom travelers and boom tensioning lines

FIG. 11 illustrates a modification to the embodiment of FIG. 9 whereinthe mast is supported by a bearing means that allows the entire mast torotate to the optimum position relative to the wind.

FIG. 12 illustrates a modification to the embodiment of FIG. 10 whereinthe mast is supported by a bearing means that allows the entire mast torotate to the optimum position relative to the wind.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an embodiment of the present invention in a powerboatconfiguration (without sails). A large upper hull 1 is suspended over aleft float hull 2 and right float hull 3 by means of four supportstructures 4. The wide support structures shown in FIG. 1 may beimproved by utilizing two or more narrow beams per support structure,which allows lateral air flow and thereby reduces lateral windage. Theimproved support structure 4 is shown in FIG. 2.

The top-view diagram in FIG. 3 illustrates the relative width of theupper hull 1 in comparison to the twin float hulls 2 and 3. The forwardand aft portions of the upper hull enclose the passenger cabins, andextend laterally beyond the longitudinal centerline of the left andright float hulls to maximize the accommodation space. The middleportion of the upper hull encloses the common areas (salon, galley,storage, etc), and is constrained to the region inboard of thelongitudinal centerline of the left and right float hulls. This uniqueconfiguration creates deck areas 5 and 6 on the top of both float hullsthereby making it safer and easier to board, dock, and access shorecraft. The deck areas also serve as recreation space and swim platforms.

FIG. 4 shows the preferred embodiment of the shore craft storage anddeployment means which includes a dinghy storage compartment door 7which can be lowered to provide access to the dinghy 8. The compartmentdoor is opened by a lowering mechanism 9 attached to the door. FIG. 5 isa perspective view showing how the dinghy can be moved out of thestorage compartment, and across the adjacent deck and into the water.

FIG. 6 shows an alternate embodiment where the dinghy 8 is lowereddirectly into the water via a lowering mechanism 9, where it may beboarded via the inboard edge of the adjacent float hull deck 6. Thelowering mechanism 9 in either embodiment is rope or synthetic lineattached to a conventional manual winch, electric winch, or equivalentmeans such as a hydraulic piston.

FIG. 7 shows the multihull watercraft in a sailing configuration. Thesailing rig includes a mast 10, a forward stay 11 and an aft stay 12.Both stays are attached to a pivoting member 13 at the top end of themast, with a bearing 14 that allows the member to rotate freely.

A forward sail 15 is suspended between the forward stay and the mast. Anaft sail 16 is suspended between the aft stay and the mast. The mannerin which the sails are attached to the mast and stays is not relevant tothe present invention, and may include any of the conventional elementssuch as bolt rope and tracks, hanks, or roller furling devices.

The bottom end of the forward stay connects to a sliding car 17 thatruns along a curved forward track 18 that is rigidly fixed to the theboat forward of the mast. Similarly, the aft stay 12 connects to an aftsliding car 19 which runs along an aft curved track 20 located aft ofthe mast. The sliding cars and track are commonly used on sailing rigsand are widely available from marine equipment suppliers, however thespecific design of the car is not important. Any type of sliding car andtrack that can withstand the tension applied by the stays may be used,thus the scope of the invention is defined by the claims and not limitedby the specification. The track can be mounted on a horizontal decksurface as shown in FIG. 7, or alternately may be mounted on theexterior surface of the upper hull.

The curved tracks 18 and 20 are shaped with a constant radius ofcurvature equal to the distance between the track and the mast, and thesliding cars are installed at opposing positions relative to the mast(180 degrees apart). This ensures that the stays do not apply anylateral force on the top of the mast, only a compression force pushingthe mast downward.

A car positioning means moves the cars to any desired location on theirtracks while still maintaing their relative positions at 180 degrees.One embodiment is illustrated in FIG. 8. A continuous control line 21runs in a loop through both tracks, then routed through a set of pulleys22 (as many as needed), and around a manual or electric winch 23 thatcan move the control line in either direction. When the winch is turnedthe sliding cars will move simultaneously, causing the stays andattached sails to rotate about the mast to a new position appropriatefor the current wind direction.

When the watercraft is sailing, the prevailing wind applies pressure onthe forward sail and aft sail simultaneously, which in turn appliespressure to the slider cars and control line. Since the cars arecontrolled by a single control line in a loop, the pressure on theforward sail counteracts the pressure on the aft sail, which means therig can be rotated even under load with only moderate force on therotation control line.

The winch 23 shown in in FIG. 8 could alternately be replaced with anupright spoked wheel 24 of the type used to steer a boat, as shown inFIG. 9. The large wheel would provide a mechanical advantage as well asinertia when in motion that allows the skipper to quickly rotate thesailing rig to a new position.

An alternate embodiment of the car positioning means could place thecontrol line alongside the track guided by pulley wheels, instead ofrunning inside the track as illustrated. Many other equivalent means maybe used to perform the same car positioning function, including linearactuators or hydraulic devices that move the control lines or carsdirectly, or electric motors that attach to the car and engage the trackusing wheels or gear teeth. Thus the scope of the invention is definedby the attached claims and their equivalent means, rather than theexamples cited.

The sailing rig described above may be enhanced in order to accommodatelarger sails for more propulsive power. FIG. 9 illustrates the sailingrig with the addition of a forward boom 25, an aft boom 26, and a mastcollar 27 with internal bearings that allow it to rotate freely aroundthe mast. The booms connect at one end to their respective stays, and tothe rotating mast collar at the other end. The car positioning meansincludes the control line loop 21 and a control wheel 24, however any ofthe alternate car positioning means mentioned previously may be used.

With the booms installed, the forward and aft stays are pushed fartheraway from the mast, which allows for larger sail area without increasingmast height or boat length. There is also the benefit that the stays areless likely to come into contact with passengers or equipment on thedeck.

The sailing rig described above can be further enhanced as shown in FIG.10. Traveler mechanisms 27 and 28 are added to the underside of theforward and aft booms (each traveler is comprised of a sliding car andtrack, but for clarity the combination of elements in this case will bedesignated as a traveler). Tensioning lines 29 and 30 connect theforward and aft travelers to the sliding cars 17 and 19 on the decktracks 18 and 20. The boom traveler effectively allows the connectingpoint to move along the boom, so the tensioning lines will always remainin a nominally vertical orientation as the sliding cars below them movealong the track.

The added elements in this configuration of the sailing rig provide twoimportant benefits. First, the deck tracks no longer need to haveconstant radius of curvature, so there's more flexibility in where theyare installed. Second, the tracks can be extended further amidships(toward the mast) to allow greater rotation of the sailing rig in eitherdirection, as illustrated in FIG. 10. This allows the boat to sail moreefficiently in a wider range of wind conditions.

In the embodiment illustrated in FIG. 9 the pivot means 14 allows theforward and aft stays to rotate around the mast. The rotating collar 27allows the booms to rotate around the mast in a similar manner. In analternate embodiment, the entire mast is supported by a mast bearingmeans 31 shown in FIG. 11. The mast bearing means is anchored within thedeck of the boat and contains ball bearings, roller bearings, orfunctionally equivalent elements and is a well-known mechanism in themarine industry. This allows the entire mast to rotate and eliminatesthe need for the pivot means (for the stays) at the top of the mast andthe rotating collar (for the booms) near the bottom of the mast. Thisenhancement provides improved aerodynamic performance when used with amast with an airfoil crosssection. Rotating the entire sailing rig tothe optimum position also puts the mast in the optimum orientation toreduce drag.

In the embodiment illustrated in FIG. 10 the pivot means 14 and rotatingcollar 27 allows the sailing rig to rotate as discussed above. In analternate embodiment, the entire mast is supported by a mast bearingmeans 31 shown in FIG. 12. This allows the entire mast to rotate, andeliminates the need for the pivot means at the top of the mast and therotating collar near the bottom of the mast. This enhancement providesimproved aerodynamic performance as discussed with the embodiment ofFIG. 11.

CONCLUSION

The patent discloses a multihull watercraft with a unique hullconfiguration providing numerous benefits, an improved means for dinghystorage and deployment, and a new simplified sailing rig that is easierto operate and maintain than the conventional Bermuda rig. The scope ofthe present is not limited to the examples provided in thespecification, but is defined by the claims.

1. A multihull watercraft including left and right parallel float hulls,an upper hull bridging the space between said float hulls, and foursupport structures connecting between the upper hull and the left andright float hulls, wherein the improvement comprises the relocation ofthe passenger cabins from within the float hulls to the forward and aftregions of the upper hull, thereby permitting hydrodynamically efficientnarrow float hulls, and wherein said forward and aft upper hull regionsextend laterally to positions beyond the longitudinal centerlines of theleft and right float hulls thereby maximizing the cabin space, andwherein the middle portion of said upper hull containing the common areais constrained laterally to a region inboard of the longitudinalcenterlines of the left and right float hulls, thereby creating spacefor deck areas on top of the left and right float hulls for the purposeof easier boarding, for recreation, and for safer and easier boarding ofshore craft.
 2. The multihull watercraft of claim 1 wherein each supportstructure is comprised of 2 or more narrow beams that allow lateral flowof air thereby reducing windage on the watercraft.
 3. The multihullwatercraft of claim 2 wherein the beams are hollow tubes made of metalor composite fiber material.
 4. The multihull watercraft of claim 1 thatincludes a storage compartment on the underside of the upper hull for adinghy, and a storage compartment door that covers the dinghycompartment, and a means to lower the door and dinghy to a positionadjacent to the left or right float hull so that the dinghy may be movedout of the storage compartment, across the top deck of the float hull,and into the water along the outside edge of the float hull.
 5. Themultihull watercraft of claim 1 that incorporates a storage compartmenton the underside of the upper hull for a dinghy and includes means tolower the dinghy directly into the water at a location adjacent to theleft or right float hull where the dinghy can be easily and safelyboarded.
 6. A multihull watercraft with a sailing rig that includes: (a)a mast, (b) a pivoting member with bearing means secured to the upperend of said mast that can rotate freely (c) a curved forward trackaffixed to the forward region of the watercraft with a radius ofcurvature equal to the distance to the mast, (d) a forward sliding carwith bearing means that allow the car to move to any position on saidforward track, (e) a curved aft track rigidly mounted to the aft regionof the watercraft with a radius of curvature equal to the distance tothe mast, (f) an aft sliding car with bearing means that allow the carto move to any position on said aft track, (g) a forward stay connectedbetween said pivoting member and the forward sliding car, (h) an aftstay connected between said pivoting member and the aft sliding car, (i)a forward sail suspended between the forward stay and the mast, (j) anaft sail suspended between the aft stay and the mast, (k) a carpositioning means that moves the sliding cars to any desired location ontheir respective tracks while maintaining the sliding cars in a relativeposition of 180 degrees apart, thereby causing the sailing rig to rotateabout the mast to achieve the optimum angle to the wind.
 7. A multihullwatercraft with a sailing rig that includes: (a) a mast, (b) a pivotingmember with bearing means secured to the upper end of said mast that canrotate freely, (c) a curved forward track mounted forward of the mastwith a radius of curvature equal to the distance to the mast, (d) aforward sliding car with bearing means that allow the car to move to anyposition on the forward track, (e) a curved aft track mounted aft of themast with a radius of curvature equal to the distance to the mast, (f)an aft sliding car with bearing means that allow the car to move to anyposition on the aft track, (g) a forward stay connected between thepivoting member and the forward sliding car, (h) an aft stay connectedbetween the pivoting member and the aft sliding car, (i) a forward sailsuspended between the forward stay and the mast, (j) an aft sailsuspended between the aft stay and the mast, (k) a mast collar locatednear the bottom of the mast with bearing means that allow the collar torotate freely, (l) a forward boom connected between the mast collar andthe forward stay such that the stay is pushed farther away from themast, (m) an aft boom connected between the mast collar and the aft staysuch that the stay is pushed farther away from the mast, (n) a carpositioning means that moves the sliding cars to any desired location ontheir respective tracks while maintaining the sliding cars in a relativeposition of 180 degrees apart, thereby causing the sailing rig to rotateabout the mast to achieve the optimum angle to the wind.
 8. A multihullwatercraft with a sailing rig that includes: (a) a mast, (b) a pivotingmember secured to the upper end of said mast with bearing means thatallow the member to rotate freely, (c) a forward track mounted forwardof the mast, (d) a forward sliding car with bearing means that allow thecar to move to any position along said forward track, (e) an aft trackmounted aft of the mast, (f) an aft sliding car with bearing means thatallow the car to move to any position along said aft track, (g) a mastcollar located near the bottom of the mast with bearing means that allowthe collar to rotate freely, (h) a forward boom whose aft end isconnected to said mast collar, (i) a forward boom traveler mounted onthe underside of the forward boom, (j) an aft boom whose forward end isconnected to said mast collar, (k) an aft boom traveler mounted on theunderside of the aft boom, (l) a forward stay connected between saidpivoting member and the forward end of the forward boom, (m) an aft stayconnected between said pivoting member and the aft end of the aft boom,(n) a forward sail suspended between the forward stay, forward boom, andthe mast, (o) an aft sail suspended between the aft stay, the aft boom,and the mast, (p) a forward boom tensioning line whose lower end isconnected to the forward sliding car, and whose upper end is connectedto said forward boom traveler, (q) an aft boom tensioning line whoselower end is connected to said aft sliding car, and whose upper end isconnected to said aft boom traveler, (r) a car positioning means thatmoves the sliding cars to any desired location on their respectivetracks while maintaining the sliding cars in a relative position of 180degrees apart, thereby causing the sailing rig to rotate about the mastto achieve the optimum angle to the wind.
 9. A multihull watercraft witha sailing rig that includes: (a) a mast, (b) a mast bearing meansanchored within the deck which supports the mast and allows freerotation in either direction, (c) a curved forward track mounted forwardof the mast with a radius of curvature equal to the distance to themast, (d) a forward sliding car with bearing means that allow the car tomove to any position on the forward track, (e) a curved aft trackmounted aft of the mast with a radius of curvature equal to the distanceto the mast, (f) an aft sliding car with bearing means that allow thecar to move to any position on the aft track, (g) a forward stayconnected between the pivoting member and the forward sliding car, (h)an aft stay connected between the pivoting member and the aft slidingcar, (i) a forward sail suspended between the forward stay and the mast,(j) an aft sail suspended between the aft stay and the mast, (k) aforward boom connected between the mast and the forward stay such thatthe stay is pushed farther away from the mast, (l) an aft boom connectedbetween the mast and the aft stay such that the stay is pushed fartheraway from the mast, (m) a car positioning means that moves the slidingcars to any desired location on their respective tracks whilemaintaining the sliding cars in a relative position of 180 degreesapart, thereby causing the sailing rig to rotate about the mast toachieve the optimum angle to the wind.
 10. A multihull watercraft with asailing rig that includes: (a)a mast, (b) a mast bearing means anchoredwithin the deck which supports the mast and allows free rotation ineither direction, (c) a forward track mounted forward of the mast, (d) aforward sliding car with bearing means that allow the car to move to anyposition along said forward track, (e) an aft track mounted aft of themast, (f) an aft sliding car with bearing means that allow the car tomove to any position along said aft track, (g) a forward boom whose aftend is connected to said mast, (h) a forward boom traveler mounted onthe underside of the forward boom, (i) an aft boom whose forward end isconnected to said mast, (j) an aft boom traveler mounted on theunderside of the aft boom, (k) a forward stay connected at or near thetop of said mast and connected to the forward end of the forward boom,(l) an aft stay connected at or near the top of said mast and connectedto the aft end of the aft boom, (m) a forward sail suspended between theforward stay, forward boom, and the mast, (n) an aft sail suspendedbetween the aft stay, the aft boom, and the mast, (o) a forward boomtensioning line whose lower end is connected to the forward sliding car,and whose upper end is connected to said forward boom traveler, (p) anaft boom tensioning line whose lower end is connected to said aftsliding car, and whose upper end is connected to said aft boom traveler,(q) a car positioning means that moves the sliding cars to any desiredlocation on their respective tracks while maintaining the sliding carsin a relative position of 180 degrees apart, thereby causing the sailingrig to rotate about the mast to achieve the optimum angle to the wind.